1. Field of the Invention
The present invention relates to an antenna apparatus of a mobile terminal. More particularly, the present invention relates to an antenna apparatus of a mobile terminal and a method for implementing characteristics of an ultra-wideband antenna of a mobile terminal using an antenna having narrow-band characteristics.
2. Description of the Related Art
With advances in mobile communication technologies and demands for various services, mobile communication services are continuously evolving. Early mobile communication services focused on simple vocal communications only. Recently, various mobile communication services, such as a multimedia service providing music and movies, a wireless mobile internet service enabling a user to have high-speed internet access and a satellite communication service providing an international roaming service are being developed. In mobile communication service technologies, ultra-wideband mobile communication using ultra-wideband technology is being developed via a Personal Communication Services (PCS) mobile communication system and a Wideband Code Division Multiple Access (WCDMA) mobile communication system, as well as other conventional cellular communication systems. If the various mobile communication services are provided to a single mobile terminal at various frequency bands, the convenience and utility mobile terminal will be increased. Hence, broadband wireless terminals are now widely used and a technology enabling an antenna of the wireless terminal to operate in a broadband environment is required.
A conventional mobile terminal has a small antenna. The small antenna provides inferior radiation efficiency, a narrow frequency band and a small gain. Thus, there is a need to develop miniaturized, multi-functional and high-performance antennas to be employed in the mobile communication system. An existing antenna of a mobile terminal is a ¼ wavelength monopole type or a helical type protruding over the mobile terminal, which is not strong and is inconvenient when transporting the mobile terminal. Research and development with respect to internal antennas is ongoing to address shortcomings of the antenna. With the miniaturization and internalization of the antenna, a Planar Inverted F Antenna (PIFA) is being implemented as an internal antenna in a mobile terminal due to a simple manufacturing process and a flat structure.
However, the internal antenna has a restriction in size when being installed into a narrow space of a mobile terminal. With the miniaturization, input impedance becomes a large capacitive reactance against low resistance. In this case, when the reactance is canceled using a matching circuit, narrow-band characteristics are exhibited. Furthermore, due to the low resistance characteristics, radiation efficiency of an antenna is significantly lowered. Since thickness of a mobile terminal must be considered in order to install the PIFA into the mobile terminal, a height restriction exists for the PIFA. However, the internal antenna has a limit for obtaining a wide broadband capability. Since the portable terminal is restricted in size, a physical limit exists in order to provide a small light ultra-wideband antenna in the portable terminal.
Therefore, a need exists for an antenna apparatus of a mobile terminal and a method for implementing characteristics of an ultra-wideband antenna of the antenna apparatus.